Louis Prevost, Pope Leo XIV's older brother who lives in Florida, has multiple myeloma, his wife told CBS News on Tuesday. The news comes amid the Vatican's earlier announcement that the pope has been diagnosed with lung cancer after undergoing surgery to remove the lower lobe of his right lung. Deborah Prevost did not share what stage Louis' cancer is in but said he's currently in a clinical trial at a local hospital where he's being treated.
Multiple myeloma is a type of cancer that affects plasma cells, according to the Multiple Myeloma Research Foundation. Deborah Prevost said Louis was first diagnosed in 2017 but was able to maintain it at a "very low level" after undergoing treatment in 2019 that included stem cell treatment and a clinical trial. He "fell out of remission" three months ago, she said.
She could not comment on the specifics of Pope Leo's condition but said her husband and his brother spoke last week before Louis went in for his clinical trial. "He called to let us know what would be happening," Deborah said. "We keep praying, keeping spirits up for both of them." Pope Leo underwent surgery Tuesday that confirmed he has lung cancer, the Vatican said earlier Tuesday.
The Vatican didn't disclose what stage the cancer was in or whether the cancer may have spread. It also did not detail what further procedures the pope may have to undergo. Deborah Prevost told CBS News the family was "going through a lot," but she was hopeful that Leo's cancer was in the very early stages.
She said she hadn't heard about any potential radiation or chemotherapy treatment. In an interview with CBS News in May 2025, after then-Cardinal Robert Prevost was chosen as the new pope, Louis Prevost said the family knew "from a very young age, there was something special about Rob." Pope Leo is the first U.S.-born leader of the Catholic Church. He grew up alongside his two older siblings, Louis and John, in the Chicago area.
"While I was out playing boy games, you know, whether it was baseball, cops and robbers, tag, flashlight, whatever kid games, Rob used to like to play priest," Louis Prevost told CBS News at the time. "Since way back then, he's had that calling." "He will always be Rob," Louis added. "If we do get over there and do get to meet him, I'm still going to treat him like my little brother.
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